Papers by Author: B.J. Duggan

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Authors: B.J. Duggan, Chong Soo Lee, R.E. Smallman
Authors: Lam Kai Tung, M.Z. Quadir, B.J. Duggan
Authors: B.J. Duggan, M.Z. Quadir, Richard Penelle
Abstract: The idea that a single subgrain is sufficient to produce a single recrystallised grain is the simplest explanation for the recrystallisation process. Likewise, a single Goss oriented grain arising from the primary recrystallisation process is the simplest unit which can give rise to a secondary Goss oriented grain. More complicated cluster models, for example subgrain coalescence is also considered feasible for primary recrystallisation, clusters of Goss oriented grains might be another mechanism for forming Goss oriented secondary grains. This paper examines the cluster theory using material which is produced by the ARMCO process which requires two stages of rolling. In order to achieve this aim it is necessary to destroy the connectivity between individual Goss oriented grains by using thin foils derived from sheet which gives a strong Goss texture on conventional annealing. The foils were sectioned from the subsurface which had a strong η fibre after primary recrystallisation, and ranged in thickness from 18μm (the average grain size after primary recrystallisation) up to 80μm, which is the approximate thickness of the η textured layer. The central layer, which had the classical {111} primary recrystallised texture, was similarly processed, but this did not produce secondary recrystallisation. The experiment followed the secondary recrystallisation process in the same area using sequential annealing in a vacuum furnace by a combination of EBSD and Channelling contrast microscopy. The data does not support the high energy boundary hypothesis nor the CSL explanation. But it is clear that connectivity is important, because when this is destroyed by the thin foil two dimensional morphology, as it is in the thinnest foil, secondary recrystallisation does not occur.
Authors: B.J. Duggan, Y.Y. Tse, G.J. Shen
Abstract: In an investigation of nucleation of recrystallisation in an Interstitial Free steel it was found that new crystals were almost always contained within the rolled-out hot band grain envelopes and were mostly equiaxed. At a later stage they grew and had an aspect ratio of 2:1 but at the completion of recrystallisation were again equiaxed. This is explained by the notion that nucleation occurs relatively frequently in certain grains, that these nuclei have very similar orientations and are thus orientation pinned within the solute and precipitate containing envelopes of the hot band grains. Provided the misorientation is small the impinged group are capable of spheroidisation provided the driving force across the pinned boundary is sufficient to overcome the pinning, because, by definition, this pinned boundary is of high angle character. The theory, as it is presented as coalescence, relies on a form of Östwald ripening and therefore provides a possible explanation of why grain growth kinetics obeys a time exponent of between 1/2 and 1/3. A similar observation of high aspect ratio grains has been made many times in the case of cold rolled copper which forms cube texture. Again, nuclei are formed in the cube bands, but these are prevented from lengthening because of orientation pinning. However, when the length of a group of such impinged nuclei is sufficient, spheroidisation will produce equiaxed grains.
Authors: Q.Z. Chen, K. Shen, G.J. Shen, B.J. Duggan
Authors: B.J. Duggan, G.J. Shen, Yong Bo Xu
Authors: B.J. Duggan, Chong Soo Lee, R.E. Smallman
Authors: B.J. Duggan, C.Y. Chung
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